Oxygen Partial Pressureoxygen Concentration - Mettler Toledo InPro 6800 Serie Instructions D'utilisation

All manuals and user guides at all-guides.com
InPro 6800 Series O Sensor 12/25 mm
2
10.7 Oxygen partial pressure –
oxygen concentration
The electrode current depends on the oxygen partial
pressure and the O permeability of the membrane –
2
but not on the O solubility in the solutions. The oxygen
2
concentration in mg O
determined directly with an electrode.
According to Henry's law the oxygen concentration is
proportional to its partial pressure (PO
CL pO a
2
a = solubility factor
If "a" is constant, the oxygen concentration can be
determined by means of the electrode. This applies at
constant temperature and with dilute aqueous
solutions such as drinking-water.
The solubility factor is strongly influenced not only by
the temperature but also by the composition of the
solution:
Medium, sat. with air
Water
4 mol/l KCI
50 % Methanol-water
Although the solubilities vary widely, the oxygen
electrode gives the same reading in all three solutions.
Thus, determination of the oxygen concentration is
only possible with constant and known solubility
factors "a".
Solubility may be determined by a Winkler titration or
the method developed by Käppeli and Fiechter.
References
– W.M. Krebs, I.A. Haddad Develp. Ind. Microbio.,
13, 113 (1972)
– H. Bühler, W. Ingold GIT 20, 977 (1976)
– W.M. Krebs, MBAA Techn. Quart. 16, 176 (1975)
– D.P. Lucero, Ana. Chem. 40, 707 (1968)
© 02 / 17 Mettler-Toledo GmbH
Printed in Switzerland
35
/l (CL) cannot therefore be
2
).
2
Solubility at
20 °C (68 °F) and 760 mm Hg
9.2 mg O /l
2
2 mg O /l
2
21.9 mg O /l
2
InPro 6800
52 200 953